Abstract: The separation process of an ethylene plant should be operated at low temperature. Therefore,a compression refrigeration system is needed to provide refrigerant. A ternary refrigeration system can provide a continuous cooling curve matching very well with the process stream cooling curve,and has higher thermodynamic efficiency,lower energy consumption than a cascaded refrigerant system. In order to analyze the energy saving potential of a ternary refrigeration system,in this paper,the ternary refrigerant system in a certain ethylene plant was analyzed by exergy analysis. From the exergy grand composite curve(EGCC),it could be found that the refrigerant configuration of the ternary refrigeration system was reasonable and the total exergy loss was small. The system is classified into four sub-systems:heat exchanger,compressor,throttle valve and flash drum sub-systems. The results of exergy losses show that the total exergy loss of the ternary refrigeration system is 24238.1kW,about 90% of which concentrates on the heat exchanger and compressor sub-systems. Furthermore,the exergy losses are divided into avoidable and inevitable exergy losses,in which the total inevitable exergy loss is 13539.9kW,and the total avoidable exergy loss is 10698.2kW. The work for energy conservation should focus on reducing the avoidable exergy loss.

Key words: systems engineering, exergy, optimal design, pinch, ethylene, ternary refrigerating system

摘要： 乙烯装置产品分离过程需要在低温下进行,为此需配置压缩制冷系统为深冷分离提供冷量。三元压缩制冷由于能提供温位连续的制冷曲线,与工艺物流降温曲线更好地匹配,相比传统的复叠制冷具有热力学效率高、制冷能耗低的特点。为了分析三元压缩制冷的节能潜力,本文对某乙烯装置的三元制冷系统进行了(火用)分析。从(火用)总复合曲线(EGCC)图的分析可以得出该系统三元冷剂配置是比较合理的,(火用)损失较小。将该制冷系统划分为换热器、压缩机、节流阀、闪蒸罐等子系统,并分别计算了各子系统的(火用)损失。三元制冷系统的(火用)损失总计为24238.1kW,90%(火用)损失集中在换热器和压缩机两个子系统。然后将(火用)损失分为可避免的和不可避免的(火用)损失两类,其中不可避免的(火用)损失为13539.9kW,可避免的(火用)损失为10698.2kW,最后指出节能重点应该放在降低可避免的(火用)损失。

关键词: 系统工程, ?, 优化设计, 夹点技术, 乙烯, 三元制冷